Organic photoelectronic device and image sensor

ABSTRACT

An organic photoelectronic device includes a first electrode and a second electrode facing each other and a light-absorption layer between the first electrode and the second electrode and including a first region closest to the first electrode, the first region having a first composition ratio (p1/n1) of a p-type semiconductor relative to an n-type semiconductor, a second region closest to the second electrode, the second region having a second composition ratio (p2/n2) of the p-type semiconductor relative to the n-type semiconductor, and a third region between the first region and the second region in a thickness direction, the third region having a third composition ratio (p3/n3) of the p-type semiconductor relative to the n-type semiconductor that is greater or less than the first composition ratio (p1/n1) and the second composition ratio (p2/n2).

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.15/156,438, filed on May 17, 2016, which claims priority to the benefitof Korean Patent Application No. 10-2015-0095356 filed in the KoreanIntellectual Property Office on Jul. 3, 2015, the entire contents ofeach of the above-referenced applications are hereby incorporated byreference.

BACKGROUND 1. Field

Example embodiments relate to an organic photoelectronic device and animage sensor.

2. Description of the Related Art

A photoelectronic device typically converts light into an electricalsignal using photoelectric effects. The photoelectronic device mayinclude a photodiode and/or a phototransistor, and may be applied to animage sensor, a solar cell and/or an organic light emitting diode.

An image sensor including a photodiode typically requires higherresolution and thus a smaller pixel. At present, a silicon photodiode iswidely used, but exhibits deteriorated sensitivity because of arelatively small absorption area due to the relatively small pixels.Accordingly, an organic material that is capable of replacing siliconhas been researched.

An organic material has a relatively high extinction coefficient andselectively absorbs light in a particular wavelength region depending ona molecular structure, and thus may simultaneously replace a photodiodeand a color filter and as a result improve sensitivity and contribute tohigher integration.

SUMMARY

Example embodiments provide an organic photoelectronic device capable ofimproving wavelength selectivity.

Example embodiments provide an image sensor including the organicphotoelectronic device.

According to example embodiments, an organic photoelectronic deviceincludes a first electrode and a second electrode facing each other, anda light-absorption layer between the first electrode and the secondelectrode. The light-absorption layer includes a first region closest tothe first electrode, a second region closest to the second electrode,and a third region between the first region and the second region in athickness direction. The first region has a first composition ratio(p₁/n₁) of a p-type semiconductor relative to an n-type semiconductor,the second region has a second composition ratio (p₂/n₂) of the p-typesemiconductor relative to the n-type semiconductor, and the third regionhas a third composition ratio (p₃/n₃) of the p-type semiconductorrelative to the n-type semiconductor that is greater or less than thefirst composition ratio (p₁/n₁) and the second composition ratio(p₂/n₂).

The first composition ratio (p₁/n₁) may be the same as the secondcomposition ratio (p₂/n₂).

The first composition ratio (p₁/n₁) may be different from the secondcomposition ratio (p₂/n₂).

A composition ratio (p/n) of the p-type semiconductor relative to then-type semiconductor of the light-absorption layer may be continuouslyincreased and then decreased along the thickness direction.

A composition ratio (p/n) of the p-type semiconductor relative to then-type semiconductor of the light-absorption layer may bediscontinuously increased and then decreased along the thicknessdirection.

A composition ratio (p/n) of the p-type semiconductor relative to then-type semiconductor of the light-absorption layer may be continuouslydecreased and then increased along the thickness direction.

A composition ratio (p/n) of the p-type semiconductor relative to then-type semiconductor of the light-absorption layer may bediscontinuously decreased and then increased along the thicknessdirection.

The light-absorption layer may be configured to absorb light in at leastone part of a visible ray wavelength region, and a maximumlight-absorption position of the light-absorption layer may be differentdepending on the visible ray wavelength region.

The visible ray wavelength region may include first visible light andsecond visible light having a different wavelength region from the firstvisible light, and the first visible light may be absorbed at a maximumin one of the first region and the second region of the light-absorptionlayer and the second visible light may be absorbed at a maximum in thethird region of the light-absorption layer.

One of the p-type semiconductor and the n-type semiconductor may be alight-absorbing material configured to selectively absorb the firstvisible light, and the other of the p-type semiconductor and the n-typesemiconductor may be a light-absorbing material configured to absorb thefirst visible light and the second visible light.

The p-type semiconductor may be the light-absorbing material configuredto selectively absorb the first visible light, the n-type semiconductormay be the light-absorbing material configured to absorb the firstvisible light and the second visible light, and the third compositionratio (p₃/n₃) may be greater than the first composition ratio (p₁/n₁)and the second composition ratio (p₂/n₂).

The third region may include the n-type semiconductor in a lesser amountthan the first region and the second region.

The n-type semiconductor may be the light-absorbing material configuredto selectively absorb the first visible light, the p-type semiconductormay be the light-absorbing material configured to absorb the firstvisible light and the second visible light, and the third compositionratio (p₃/n₃) may be less than the first composition ratio (p₁/n₁) andthe second composition ratio (p₂/n₂).

The third region may include the p-type semiconductor in a lesser amountthan the first region and the second region.

The first visible light may have a wavelength region of about 500 nm toabout 600 nm, and the second visible light may have a wavelength regionof greater than or equal to about 380 nm and less than 500 nm.

One of the p-type semiconductor and the n-type semiconductor may includeone of C60, C70, a derivative thereof, and a combination thereof.

According to example embodiments, an image sensor includes the organicphotoelectronic device.

The light-absorption layer may be configured to absorb light in at leastone part of a visible ray wavelength region, the visible ray wavelengthregion may include first visible light, second visible light, and thirdvisible light, each of the first, second and third visible light havinga different wavelength region, the organic photoelectronic device may beconfigured to selectively absorb the first visible light, and the imagesensor may further include a semiconductor substrate integrated with aplurality of first photo-sensing devices configured to sense the secondvisible light and a plurality of second photo-sensing devices configuredto sense the third visible light.

The plurality of first photo-sensing devices and the plurality of secondphoto-sensing devices may be spaced apart from each other in ahorizontal direction.

The image sensor may further include a first color filter overlappingthe plurality of first photo-sensing devices and configured toselectively transmit the second visible light, and a second color filteroverlapping the plurality of second photo-sensing devices and configuredto selectively transmit the third visible light.

The plurality of first photo-sensing devices and the plurality of secondphoto-sensing devices may be spaced apart from each other in a verticaldirection.

The light-absorption layer may be configured to absorb light in at leastone part of a visible ray wavelength region, the visible ray wavelengthregion may include first visible light, second visible light, and thirdvisible light, each of the first, second and third visible light havinga different wavelength region, the organic photoelectronic device may bea first organic photoelectronic device configured to selectively absorbthe first visible light, the image sensor may further include a secondorganic photoelectronic device configured to selectively absorb thesecond visible light and a third organic photoelectronic deviceconfigured to selectively absorb the third visible light, and the firstorganic photoelectronic device, the second organic photoelectronicdevice, and the third organic photoelectronic device may be sequentiallystacked.

The first visible light may have a wavelength region of about 500 nm toabout 600 nm, the second visible light may have a wavelength region ofgreater than or equal to about 380 nm and less than 500 nm, and thethird visible light may have a wavelength region of greater than about600 nm and less than or equal to about 780 nm.

According to example embodiments, an electronic device includes theimage sensor.

According to example embodiments, an organic photoelectronic deviceincludes a first electrode, a first light-absorption layer on the firstelectrode, the first light-absorption layer having a first compositionratio (p₁/n₁) of a p-type semiconductor relative to an n-typesemiconductor, a second light-absorption layer on the firstlight-absorption layer, the second light-absorption layer having asecond composition ratio (p₂/n₂) of the p-type semiconductor relative tothe n-type semiconductor different from the first composition ratio(p₁/n₁), a third light-absorption layer on the second light-absorptionlayer, the third light-absorption layer having the first compositionratio (p₁/n₁), and a second electrode on the third light-absorptionlayer.

The second composition ratio (p₂/n₂) may be greater than the firstcomposition ratio (p₁/n₁).

The second light-absorption layer may include the n-type semiconductorin a lesser amount than the first light-absorption layer and the thirdlight-absorption layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing an organic photoelectronicdevice according to example embodiments,

FIG. 2 is a cross-sectional view showing the light-absorption layer ofthe organic photoelectronic device of FIG. 1,

FIGS. 3 to 6 show examples of changes of composition ratios of thep-type semiconductor and the n-type semiconductor in the first to thirdregions of the light-absorption layer of FIG. 2, respectively,

FIG. 7 is a cross-sectional view showing an organic photoelectronicdevice according to example embodiments,

FIG. 8 is a schematic top plan view showing an organic CMOS image sensoraccording to example embodiments,

FIG. 9 is a cross-sectional view showing one example of the organic CMOSimage sensor of FIG. 8,

FIG. 10 is a cross-sectional view showing another example of the organicCMOS image sensor of FIG. 8,

FIG. 11 is a schematic top plan view showing an organic CMOS imagesensor according to example embodiments,

FIG. 12 is a cross-sectional view showing an organic CMOS image sensorof FIG. 11,

FIG. 13 is a graph showing external quantum efficiency depending on awavelength of the organic photoelectronic devices according to Example 1and Comparative Example 1,

FIG. 14 is a graph showing external quantum efficiency in a greenwavelength region and a blue wavelength region of the organicphotoelectronic devices according to Example 1 and Comparative Example1,

FIG. 15 is a graph showing external quantum efficiency in a greenwavelength region and a blue wavelength region of the organicphotoelectronic devices according to Comparative Examples 2 and 3,

FIG. 16 is a simulation result of an absorption wavelength regiondepending on a position of light-absorption layer of the organicphotoelectronic device according to Example 2,

FIG. 17 is a simulation result of an absorption wavelength regiondepending on a position of light-absorption layer of the organicphotoelectronic device according to Comparative Example 4,

FIG. 18 is a graph showing color shifts and YSNR10 of image sensors towhich the organic photoelectronic devices according to Example 1 andComparative Example 1 are applied, and

FIG. 19 shows light absorption curves of the p-type semiconductor andthe n-type semiconductor depending on a wavelength in the organicphotoelectronic devices according to Examples 1 to 3 and ComparativeExamples 1 to 5.

DETAILED DESCRIPTION

Example embodiments will hereinafter be described in detail, and may bemore easily performed by those who have common knowledge in the relatedart. However, this disclosure may be embodied in many different formsand is not to be construed as limited to the example embodiments setforth herein.

In the drawings, the thickness of layers, films, panels, regions, etc.,are exaggerated for clarity. It will be understood that when an elementsuch as a layer, film, region, or substrate is referred to as being “on”another element, it can be directly on the other element or interveningelements may also be present. In contrast, when an element is referredto as being “directly on” another element, there are no interveningelements present.

In the drawings, parts having no relationship with the description areomitted for clarity of the embodiments, and the same or similarconstituent elements are indicated by the same reference numeralsthroughout the specification.

It should be understood that, although the terms first, second, third,etc. may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers, and/or sections should not be limited by these terms. Theseterms are only used to distinguish one element, component, region,layer, or section from another region, layer, or section. Thus, a firstelement, component, region, layer, or section discussed below could betermed a second element, component, region, layer, or section withoutdeparting from the teachings of example embodiments.

Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,”“upper,” and the like) may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It should be understood thatthe spatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” may encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

The terminology used herein is for the purpose of describing variousembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an,” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“includes,” “including,” “comprises,” and/or “comprising,” when used inthis specification, specify the presence of stated features, integers,steps, operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Example embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of exampleembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, example embodiments should not be construed aslimited to the shapes of regions illustrated herein but are to includedeviations in shapes that result, for example, from manufacturing.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments belong. Itwill be further understood that terms, including those defined incommonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand will not be interpreted in an idealized or overly formal senseunless expressly so defined herein.

Hereinafter, an organic photoelectronic device according to exampleembodiments is described with reference to drawings.

FIG. 1 is a cross-sectional view showing an organic photoelectronicdevice according to example embodiments, and FIG. 2 is a cross-sectionalview of the light-absorption layer of the organic photoelectronic deviceof FIG. 1.

Referring to FIG. 1, an organic photoelectronic device 100 according toexample embodiments includes a first electrode 10 and a second electrode20 facing each other, and a light-absorption layer 30 between the firstelectrode 10 and the second electrode 20.

One of the first electrode 10 and the second electrode 20 is an anodeand the other is a cathode. At least one of the first electrode 10 andthe second electrode 20 may be a light-transmitting electrode, and thelight-transmitting electrode may be made of, for example, a conductiveoxide (e.g., indium tin oxide (ITO) or indium zinc oxide (IZO)), or ametal thin layer of a thin monolayer or multilayer. When one of thefirst electrode 10 and the second electrode 20 is anon-light-transmitting electrode, the non-light-transmitting electrodemay be made of, for example, an opaque conductor (e.g., aluminum (Al)).

For example, the first electrode 10 and the second electrode 20 may belight-transmitting electrodes.

The light-absorption layer 30 includes a p-type semiconductor and ann-type semiconductor to form a pn junction, and absorbs external lightto generate excitons and then separates the generated excitons intoholes and electrons.

The light-absorption layer 30 may absorb light in at least one part of awavelength region of a visible ray, and may selectively absorb, forexample a part of green light of about 500 nm to about 600 nm, bluelight of greater than or equal to about 380 nm and less than about 500nm, and red light of greater than about 600 nm and less than or equal toabout 780 nm.

At least one of the p-type semiconductor and the n-type semiconductormay be a light-absorbing material selectively absorbing one of greenlight, blue light, and red light.

For example, one of the p-type semiconductor and the n-typesemiconductor may be a light-absorbing material selectively absorbingone of green light, blue light, and red light, and the other of thep-type semiconductor and the n-type semiconductor may be alight-absorbing material selectively absorbing two or more of greenlight, blue light, and red light.

For example, one of the p-type semiconductor and the n-typesemiconductor may be a light-absorbing material selectively absorbinggreen light and the other of the p-type semiconductor and the n-typesemiconductor may be a light-absorbing material selectively absorbingblue light and/or red light together with the green light.

For example, the p-type semiconductor may be a light-absorbing materialselectively absorbing green light and the n-type semiconductor may be alight-absorbing material selectively absorbing blue light and/or redlight together with the green light.

For example, the n-type semiconductor may be a light-absorbing materialselectively absorbing green light and the p-type semiconductor may be alight-absorbing material selectively absorbing blue light and/or redlight together with the green light.

For example, the p-type semiconductor may be a light-absorbing materialselectively absorbing green light and the n-type semiconductor may be alight-absorbing material selectively absorbing blue light together withthe green light.

For example, the n-type semiconductor may be a light-absorbing materialselectively absorbing green light and the p-type semiconductor may be alight-absorbing material selectively absorbing blue light together withthe green light.

The light-absorbing material selectively absorbing green light may be,for example, quinacridone or a derivative thereof, sub-phthalocyanine ora derivative thereof and the light-absorbing material absorbing greenlight and blue light may be, for example C60, C70, a derivative thereof,or a combination thereof. However, they are not limited thereto.

The light-absorption layer 30 may mainly absorb light in a differentwavelength region depending on its region, for example, in a differentwavelength region along the thickness direction of the light-absorptionlayer 30. For example, green light may mainly be absorbed in a closerregion to the incident side of the light-absorption layer 30, and bluelight may mainly be absorbed in its middle region, namely an insideregion of the light-absorption layer 30.

In example embodiments, the p-type semiconductor and/or the n-typesemiconductor may differently be distributed depending on a region wherelight in each wavelength region is mainly absorbed, considering that theabsorption position of the light-absorption layer 30 is differentdepending on the wavelength region of a visible ray. Accordingly,wavelength selectivity may be increased by adjusting the absorptionwavelength region of the light-absorption layer 30 and thus reinforcingabsorption in a desired wavelength region but suppressing absorption inan undesired wavelength region.

The light-absorption layer 30 may include a bulk heterojunction of thep-type semiconductor and the n-type semiconductor, and a mixing ratio ofthe p-type semiconductor and the n-type semiconductor, that is, a p/ncomposition ratio (p/n ratio) may be controlled to be differentdepending on a position of the light-absorption layer 30. Herein, thep/n composition ratio may be defined as the volume of the p-typesemiconductor relative to the volume of the n-type semiconductor. Thep/n composition ratio may have an influence on an absorption rate andefficiency.

The light-absorption layer 30 may include a plurality of regions havinga different p/n composition ratio along the thickness direction. Forexample, referring to FIG. 2, the light-absorption layer 30 may includea first region 30 a, a second region 30 b, and a third region 30 cbetween the first region 30 a and the second region 30 b. For example,the first region 30 a may be a region nearest to the first electrode 10and the second region 30 b may be a region nearest to the secondelectrode 20. The first region 30 a or the second region 30 b may becloser to an incident side, and the third region 30 c may be a middleregion of the light-absorption layer 30.

The third region 30 c may have a different p/n composition ratio fromthose of the first region 30 a and the second region 30 b, and the p/ncomposition ratio of the third region 30 c may be smaller or larger thanthose of the first region 30 a and the second region 30 b.

For example, when a composition ratio of the volume of the p-typesemiconductor relative to the volume of the n-type semiconductor of thefirst region 30 a is referred to p₁/n₁, a composition ratio of thevolume of the p-type semiconductor relative to the volume of the n-typesemiconductor of the second region 30 b is referred to as p₂/n₂, and acomposition ratio of the volume of the p-type semiconductor relative tothe volume of the n-type semiconductor of the third region 30 c isreferred to as p₃/n₃, the composition ratios of the first region 30 a,the second region 30 b, and the third region 30 c of thelight-absorption layer 30 may satisfy Relationship Equations 1 and 2.

p ₃ /n ₃ >p ₁ /n ₁  [Relationship Equation 1]

p ₃ /n ₃ >p ₂ /n ₂  [Relationship Equation 2]

For example, Relationship Equations 1 and 2 may be applied when thep-type semiconductor is a light-absorbing material selectively absorbinggreen light and the n-type semiconductor is a light-absorbing materialabsorbing green light and blue light. In example embodiments, absorptionof blue light of the n-type semiconductor may be reduced and externalquantum efficiency (EQE) of blue light may be also reduced by relativelyincreasing the volume of the p-type semiconductor relative to the volumeof the n-type semiconductor in a middle region of the light-absorptionlayer 30 mainly absorbing blue light, that is the third region 30 c.Accordingly, green wavelength selectivity of the light-absorption layer30 may be increased.

For example, Relationship Equations 1 and 2 may be satisfied by reducingthe content of the n-type semiconductor of the third region 30 c, whilethe first region 30 a, the second region 30 b, and the third region 30 cmaintain the same content of the p-type semiconductor.

For another example, a composition ratio of the first region 30 a, thesecond region 30 b, and the third region 30 c of the light-absorptionlayer 30 may satisfy Relationship Equations 3 and 4.

p ₃ /n ₃ <p ₁ /n ₁  [Relationship Equation 3]

p ₃ /n ₃ <p ₂ /n ₂  [Relationship Equation 4]

For example, Relationship Equations 3 and 4 may be applied when then-type semiconductor is a light-absorbing material selectively absorbinggreen light and the p-type semiconductor is a light-absorbing materialabsorbing green light and blue light. Herein, the volume of the p-typesemiconductor relative to the volume of the n-type semiconductor in themiddle region of the light-absorption layer 30 mainly absorbing bluelight, that is, the third region 30 c may be relatively reduced todecrease absorption of blue light by the n-type semiconductor and also,external quantum efficiency (EQE) of the blue light. Accordingly, greenwavelength selectivity of the light-absorption layer 30 may beincreased.

For example, Relationship Equations 3 and 4 may be satisfied by reducingthe content of the p-type semiconductor in the third region 30 c, whilethe first region 30 a, the second region 30 b, and the third region 30 cmay maintain the same content of the n-type semiconductor.

When Relationship Equations 1 and 2 or 3 and 4 may be satisfied, theratio (p₁/n₁) of the volume of the p-type semiconductor of the firstregion 30 a relative to the volume of the n-type semiconductor may bethe same as or different from the ratio (p₂/n₂) of the volume of thep-type semiconductor of the second region 30 b relative to the volume ofthe n-type semiconductor, and the composition ratios of the first region30 a and the second region 30 b of the light-absorption layer 30 maysatisfy one of Relationship Equations 5 to 7.

p ₁ /n ₁ =p ₂ /n ₂  [Relationship Equation 5]

p ₁ /n ₁ >p ₂ /n ₂  [Relationship Equation 6]

p ₁ /n ₁ <p ₂ /n ₂  [Relationship Equation 7]

For example, the first region 30 a, the second region 30 b, and thethird region 30 c of the light-absorption layer 30 may have acomposition ratio satisfying one of Relationship Equations 8 to 10.

p ₃ /n ₃ >p ₁ /n ₁ =p ₂ /n ₂  [Relationship Equation 8]

p ₃ /n ₃ >p ₁ /n ₁ >p ₂ /n ₂  [Relationship Equation 9]

p ₃ /n ₃ >p ₂ /n ₂ >p ₁ /n ₁  [Relationship Equation 10]

For another example, the first region 30 a, the second region 30 b, andthe third region 30 c of the light-absorption layer 30 may have acomposition ratio satisfying Relationship Equations 11 to 13.

p ₃ /n ₃ <p ₁ /n ₁ =p ₂ /n ₂  [Relationship Equation 11]

p ₃ /n ₃ <p ₁ /n ₁ <p ₂ /n ₂  [Relationship Equation 12]

p ₃ /n ₃ <p ₂ /n ₂ <p ₁ /n ₁  [Relationship Equation 13]

FIGS. 3 to 6 show examples of changes of composition ratios of thep-type semiconductor and the n-type semiconductor in the first to thirdregions 30 a, 30 b, and 30 c of the light-absorption layer of FIG. 2,respectively

Referring to FIGS. 3 and 4, a p/n composition ratio of thelight-absorption layer 30 may be discontinuously or continuouslyincreased and then decreased along the thickness direction of thelight-absorption layer 30.

Specifically, referring to FIG. 3, the third region 30 c may have alarger p/n composition ratio than those of the first region 30 a and thesecond region 30 b, and thus the p/n composition ratio of thelight-absorption layer 30 may be discontinuously increased and then,decreased along the first region 30 a, the third region 30 c, and thesecond region 30 b. Herein, the term of ‘discontinuous’ may mean to haveat least one intermittent point and include all the changes except for agradual or continuous change.

In FIG. 3, the first region 30 a has a constant p/n composition ratioalong the thickness direction, the second region 30 b has a constant p/ncomposition ratio along the thickness direction, and the third region 30c has a constant p/n composition ratio along the thickness direction,but is not limited thereto, and thus the p/n composition ratio in thefirst region 30 a, the second region 30 b or the third region 30 c maybe changed.

Referring to FIG. 4, the third region 30 c may have a larger p/ncomposition ratio than those of the first region 30 a and the secondregion 30 b, and thus the p/n composition ratio of the light-absorptionlayer 30 may be continuously increased and then, decreased along thefirst region 30 a, the third region 30 c, and the second region 30 b.Herein, the term of ‘continuous’ may mean gradually changed at aconstant or inconstant rate.

Referring to FIGS. 5 and 6, the p/n composition ratio of thelight-absorption layer 30 may be discontinuously or continuouslydecreased and then, increased along the thickness direction of thelight-absorption layer 30.

Specifically, referring to FIG. 5, the third region 30 c may have asmaller than those of the first region 30 a and the second region 30 b,and the p/n composition ratio may be discontinuously decreased and then,increased along the first region 30 a, the third region 30 c, and thesecond region 30 b. In FIG. 5, each first region 30 a, second region 30b, and third region 30 c has a constant p/n composition ratio but is notlimited thereto, and the p/n composition ratio in each first region 30a, second region 30 b, and third region 30 c may be changed.

Referring to FIG. 6, the third region 30 c has a smaller p/n compositionratio than those of the first region 30 a and the second region 30 b,and thus the p/n composition ratio of the light-absorption layer 30 maybe continuously decreased and then, increased along the first region 30a, the third region 30 c, and the second region 30 b.

In this way, wavelength selectivity may be increased by changing the p/ncomposition ratio along the thickness direction of the light-absorptionlayer 30 and thus reinforcing absorption in a desired wavelength regionand suppressing absorption in an undesired wavelength region,considering that the absorption region of the light-absorption layer 30is changed depending on wavelength region of a visible ray in exampleembodiments.

Specifically, the external quantum efficiency (EQE) of the organicphotoelectronic device 100 may be proportional to the absorbance andinternal quantum efficiency (IQE) of the light-absorption layer 30, andthe internal quantum efficiency (IQE) may be classified into chargeseparation efficiency (CS) and charge collection efficiency (CC).

According to example embodiments, light absorbance and charge separationefficiency in the desired wavelength region may be secured by includingthe p-type semiconductor and the n-type semiconductor in a p/ncomposition ratio capable of exerting an optimal efficiency of absorbinglight in the desired wavelength region. Simultaneously, light absorbanceand charge separation efficiency in the undesired wavelength region maybe reduced by changing the p/n composition ratio into a p/n compositionratio capable of decreasing efficiency of absorbing light in theundesired wavelength region. Accordingly, wavelength selectivity may beincreased by securing light absorbance and external quantum efficiency(EQE) in the desired wavelength region and simultaneously suppressinglight absorbance and external quantum efficiency in the undesiredwavelength region.

The light-absorption layer 30 may include the p-type semiconductor andthe n-type semiconductor in a volume ratio of about 10:1 to about 1:10,for example, about 8:2 to about 2:8 or about 6:4 to about 4:6.

The third region 30 c of the light-absorption layer may have about 5% to80% larger or smaller p/n composition ratio, about 10% to 60% larger orsmaller p/n composition ratio within the range, and about 10% to 50%larger or smaller p/n composition within the range than that of thefirst region 30 a or the second region 30 b.

The light-absorption layer 30 may be an intrinsic layer (I layer), andmay further include a p-type layer and/or an n-type layer on one side orboth sides of the light-absorption layer 30. For example, the organicphotoelectronic device 100 may include various combinations of a p-typelayer/I layer, an I layer/n-type layer, a p-type layer/I layer/n-typelayer, etc., between the first electrode 10 and the second electrode 20.The p-type layer may include a p-type semiconductor and the n-type layermay include an n-type semiconductor.

The light-absorption layer 30 may have a thickness of about 1 nm toabout 500 nm, and for example, about 5 nm to about 300 nm. When thelight-absorption layer 30 has a thickness within the range, thelight-absorption layer 30 may effectively absorb light, effectivelyseparate holes from electrons, and deliver them, thereby effectivelyimproving photoelectronic conversion efficiency.

In the organic photoelectronic device 100, when light enters from thefirst electrode 10 and/or second electrode 20, and when thelight-absorption layer 30 absorbs light having a given or predeterminedwavelength region, excitons may be produced from the inside. Theexcitons are separated into holes and electrons in the light-absorptionlayer 30, and the separated holes are transported to an anode that isone of the first electrode 10 and second electrode 20 and the separatedelectrons are transported to the cathode that is the other of and thefirst electrode 10 and second electrode 20 so as to flow a current inthe organic photoelectronic device.

Hereinafter, an organic photoelectronic device according to exampleembodiments is illustrated.

FIG. 7 is a cross-sectional view showing an organic photoelectronicdevice according to example embodiments.

Referring to FIG. 7, an organic photoelectronic device 200 includes afirst electrode 10 and a second electrode 20 facing each other, and thelight-absorption layer 30 between the first electrode 10 and the secondelectrode 20, like the example embodiment illustrated in FIG. 1. Thefirst electrode 10, the second electrode 20, and the light-absorptionlayer 30 are the same as described above.

However, the organic photoelectronic device 200 according to exampleembodiments further includes charge auxiliary layers 40 and 50 betweenthe first electrode 10 and the light-absorption layer 30 and the secondelectrode 20 and the light-absorption layer 30, unlike the exampleembodiment illustrated in FIG. 1. The charge auxiliary layers 40 and 50may facilitate the transfer of holes and electrons separated from thelight-absorption layer 30, so as to increase efficiency.

The charge auxiliary layers 40 and 50 may be at least one selected froma hole injection layer (HIL) for facilitating hole injection, a holetransport layer (HTL) for facilitating hole transport, an electronblocking layer (EBL) for preventing or inhibiting electron transport, anelectron injection layer (EIL) for facilitating electron injection, anelectron transport layer (ETL) for facilitating electron transport, anda hole blocking layer (HBL) for preventing or inhibiting hole transport.

The charge auxiliary layers 40 and 50 may include, for example, anorganic material, an inorganic material, or an organic/inorganicmaterial. The organic material may be an organic compound having hole orelectron characteristics, and the inorganic material may be, forexample, a metal oxide, e.g., molybdenum oxide, tungsten oxide, nickeloxide, etc.

The hole transport layer (HTL) may include one selected from, forexample, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS), polyarylamine, poly(N-vinylcarbazole), polyaniline,polypyrrole, N,N,N′,N′-tetrakis(4-methoxyphenyl)-benzidine (TPD),4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD), m-MTDATA,4,4′,4″-tris(N-carbazolyl)-triphenylamine (TCTA), and a combinationthereof, but is not limited thereto.

The electron blocking layer (EBL) may include one selected from, forexample, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS), polyarylamine, poly(N-vinylcarbazole), polyaniline,polypyrrole, N,N,N′,N′-tetrakis(4-methoxyphenyl)-benzidine (TPD),4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD), m-MTDATA,4,4′,4″-tris(N-carbazolyl)-triphenylamine (TCTA), and a combinationthereof, but is not limited thereto.

The electron transport layer (ETL) may include one selected from, forexample, 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA),bathocuproine (BCP), LiF, Alq₃, Gaq₃, Inq₃, Znq₂, Zn(BTZ)₂, BeBq₂, and acombination thereof, but is not limited thereto.

The hole blocking layer (HBL) may include one selected from, forexample, 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA),bathocuproine (BCP), LiF, Alq₃, Gaq₃, Inq₃, Znq₂, Zn(BTZ)₂, BeBq₂, and acombination thereof, but is not limited thereto.

Either one of the charge auxiliary layers 40 and 50 may be omitted.

The organic photoelectronic device may be applied to a solar cell, animage sensor, a photo-detector, a photo-sensor, and an organic lightemitting diode (OLED), but is not limited thereto.

The organic photoelectronic device may be for example applied to animage sensor.

Hereinafter, an example of an image sensor including the organicphotoelectronic device is described referring to drawings. As an exampleof an image sensor, an organic CMOS image sensor is illustrated.

FIG. 8 is a schematic top plan view of an organic CMOS image sensoraccording to example embodiments and FIG. 9 is a cross-sectional viewshowing one example of the organic CMOS image sensor of FIG. 8.

Referring to FIGS. 8 and 9, an organic CMOS image sensor 300 accordingto example embodiments includes a semiconductor substrate 110 integratedwith photo-sensing devices 50B and 50R, a transmission transistor (notshown), and a charge storage device 55, a lower insulation layer 60, acolor filter layer 70, an upper insulation layer 80, and an organicphotoelectronic device 100.

The semiconductor substrate 110 may be a silicon substrate, and isintegrated with the photo-sensing devices 50B and 50R, the transmissiontransistor (not shown), and the charge storage device 55. Thephoto-sensing devices 50R and 50B may be photodiodes.

The photo-sensing devices 50B and 50R, the transmission transistor,and/or the charge storage device 55 may be integrated in each pixel, andas shown in the drawing, the photo-sensing devices 50B and 50R may beincluded in a blue pixel and a red pixel and the charge storage device55 may be included in a green pixel.

The photo-sensing devices 50B and 50R sense light, the informationsensed by the photo-sensing devices may be transferred by thetransmission transistor, and the charge storage device 55 iselectrically connected with the organic photoelectronic device 100, sothe information of the charge storage 55 may be transferred by thetransmission transistor.

A metal wire (not shown) and a pad (not shown) are formed on thesemiconductor substrate 110. In order to decrease signal delay, themetal wire and pad may be made of a metal having relatively lowresistivity, for example, aluminum (Al), copper (Cu), silver (Ag), andalloys thereof, but is not limited thereto. However, example embodimentsare not limited to the structure illustrated, and the metal wire and padmay be positioned under the photo-sensing devices 50B and 50R.

The lower insulation layer 60 is formed on the metal wire and the pad.The lower insulation layer 60 may be made of an inorganic insulatingmaterial (e.g., a silicon oxide and/or a silicon nitride), or a lowdielectric constant (low K) material (e.g., SiC, SiCOH, SiCO, and SiOF).The lower insulation layer 60 has a trench exposing the charge storage55. The trench may be filled with fillers.

A color filter layer 70 is formed on the lower insulation layer 60. Thecolor filter layer 70 includes a blue filter 70B formed in the bluepixel and a red filter 70R filled in the red pixel. In exampleembodiments, a green filter is not included, but a green filter may befurther included.

The upper insulation layer 80 is formed on the color filter layer 70.The upper insulation layer 80 eliminates a step caused by the colorfilter layer 70 and smoothes the surface. The upper insulation layer 80and lower insulation layer 60 may include a contact hole (not shown)exposing a pad, and a through-hole 85 exposing the charge storage device55 of a green pixel.

The organic photoelectronic device 100 is formed on the upper insulationlayer 80. The organic photoelectronic device 100 includes the firstelectrode 10, the light-absorption layer 30, and the second electrode 20as described above.

The first electrode 10 and the second electrode 20 may be transparentelectrodes, and the light-absorption layer 30 is the same as describedabove. The light-absorption layer 30 may selectively absorb light in agreen wavelength region and replace a color filter of a green pixel.

When light enters from the second electrode 20, the light in a greenwavelength region may be mainly absorbed in the light-absorption layer30 and photoelectrically converted, while the light in the rest of thewavelength regions passes through the first electrode 10 and may besensed in photo-sensing devices 50B and 50R.

As described above, the organic photoelectronic device configured toselectively absorb light in a green wavelength region has a stackstructure, and thus the size of an image sensor may be reduced torealize a down-sized image sensor. In addition, as described above, acrosstalk due to unnecessary adsorption of light in other wavelengthregions except green may be reduced and sensitivity of an image sensormay be increased by improving green wavelength selectivity in thelight-absorption layer 30 of the organic photoelectronic device 100.

In FIG. 9, the organic photoelectronic device 100 of FIG. 1 is included,but example embodiments not limited thereto, and thus the organicphotoelectronic device 200 of FIG. 7 may be applied in the same manner.

In FIGS. 8 and 9, a stack structure where an organic photoelectronicdevice configured to selectively absorb light in a green wavelengthregion is stacked is exemplarily illustrated, but the present disclosureis not limited thereto. The present disclosure may have a structurewhere an organic photoelectronic device configured to selectively absorblight in a blue wavelength region is stacked and a green photo-sensingdevice and a red photo-sensing device may be integrated in thesemiconductor substrate 110, or a structure where an organicphotoelectronic device configured to selectively absorb light in a redwavelength region is stacked and a green photo-sensing device and a bluephoto-sensing device may be integrated in the semiconductor substrate110.

FIG. 10 is a cross-sectional view showing another example of the organicCMOS image sensor of FIG. 8.

The organic CMOS image sensor 400 according to example embodimentsincludes a semiconductor substrate 110 integrated with photo-sensingdevices 50B and 50R, a transmission transistor (not shown), and a chargestorage 55, an upper insulation layer 80, and an organic photoelectronicdevice 100, like the example embodiment as illustrated in FIG. 10.

The organic CMOS image sensor 400 according to example embodimentsincludes the blue photo-sensing device 50B and the red photo-sensingdevice 50R stacked in a vertical direction and a color filter layer 70is omitted. The blue photo-sensing device 50B and the red photo-sensingdevice 50R are electrically connected with the charge storage device(not shown) and may be transferred by the transmission transistor. Theblue photo-sensing device 50B and the red photo-sensing device 50R mayselectively absorb light in each wavelength region according to a stackdepth.

As described above, the organic photoelectronic device configured toselectively absorb light in a green wavelength region has a stackstructure and the red photo-sensing device and the blue photo-sensingdevice are stacked. Thus, the size of an image sensor may be reduced torealize a down-sized image sensor. In addition, as described above, acrosstalk due to unnecessary adsorption of light in other wavelengthregions except green may be reduced and sensitivity may be increased byimproving green wavelength selectivity in the light-absorption layer 30of the organic photoelectronic device 100.

In FIG. 10, the organic photoelectronic device 100 of FIG. 1 isincluded, but example embodiments are not limited thereto, and thus theorganic photoelectronic device 200 of FIG. 7 may be applied in the samemanner.

In FIG. 10, a stack structure where an organic photoelectronic deviceconfigured to selectively absorb light in a green wavelength region isstacked is illustrated, but the present disclosure is not limitedthereto. The present disclosure may have a structure where an organicphotoelectronic device configured to selectively absorb light in a bluewavelength region is stacked and a green photo-sensing device and a redphoto-sensing device may be integrated in the semiconductor substrate110, or a structure where an organic photoelectronic device configuredto selectively absorb light in a red wavelength region is stacked and agreen photo-sensing device and a blue photo-sensing device may beintegrated in the semiconductor substrate 110.

FIG. 11 is a schematic top plan view showing an organic CMOS imagesensor according to example embodiments and FIG. 12 is a cross-sectionalview of an organic CMOS image sensor of FIG. 11.

The organic CMOS image sensor 500 according to example embodimentsincludes a green photoelectronic device configured to selectively absorblight in a green wavelength region, a blue photoelectronic deviceconfigured to selectively absorb light in a blue wavelength region, anda red photoelectronic device configured to selectively absorb light in agreen wavelength region, and they are stacked.

The organic CMOS image sensor 500 according to the example embodimentsincludes a semiconductor substrate 110, a lower insulation layer 60, anintermediate insulation layer 70, an upper insulation layer 80, a firstorganic photoelectronic device 100 a, a second organic photoelectronicdevice 100 b, and a third organic photoelectronic device 100 c.

The semiconductor substrate 110 may be a silicon substrate, and isintegrated with the transmission transistor (not shown) and the chargestorage devices 55 a, 55 b, and 55 c.

A metal wire (not shown) and a pad (not shown) are formed on thesemiconductor substrate 110, and the lower insulation layer 60 is formedon the metal wire and the pad.

The first organic photoelectronic device 100 a is formed on the lowerinsulation layer 60.

The first organic photoelectronic device 100 a includes a firstelectrode 10 a and a second electrode 20 a facing each other and alight-absorption layer 30 a between the first electrode 10 a and thesecond electrode 20 a. One of the first electrode 10 a and the secondelectrode 20 a may be an anode and the other may be a cathode. Thelight-absorption layer 30 a may selectively absorb light in one of red,blue, and green wavelength regions. For example, the first organicphotoelectronic device 100 a may be a red photoelectronic device.

The second organic photoelectronic device 100 b is formed on theintermediate insulation layer 70.

The second organic photoelectronic device 100 b is formed on theintermediate insulation layer 70.

The second organic photoelectronic device 100 b includes a firstelectrode 10 b and a second electrode 20 b facing each other and alight-absorption layer 30 b between the first electrode 10 b and thesecond electrode 20 b. One of the first electrode 10 b and the secondelectrode 20 b may be an anode and the other may be a cathode. Thelight-absorption layer 30 b may selectively absorb light in one of red,blue, and green wavelength regions. For example, the second organicphotoelectronic device 100 b may be a blue photoelectronic device.

The upper insulation layer 80 is formed on the second organicphotoelectronic device 100 b. The lower insulation layer 60, theintermediate insulation layer 70, and the upper insulation layer 80 havea plurality of through-holes exposing the charge storages 55 a, 55 b,and 55 c.

The third organic photoelectronic device 100 c is formed on the upperinsulation layer 80. The third organic photoelectronic device 100 cincludes a first electrode 10 c and a second electrode 20 c and thelight-absorption layer 30 c between the first electrode 10 c and thesecond electrode 20 c. One of the first electrode 10 c and the secondelectrode 20 c may be an anode and the other may be a cathode. Thelight-absorption layer 30 c may selectively absorb light in one of red,blue, and green wavelength regions. For example, the third organicphotoelectronic device 100 c may be a green photoelectronic device.

At least one of the light-absorption layer 30 a of the first organicphotoelectronic device 100 a, the light-absorption layer 30 b of thesecond organic photoelectronic device 100 b, and the light-absorptionlayer 30 c of the third organic photoelectronic device 100 c may includethe p-type semiconductor and the n-type semiconductor in a differentcomposition ratio depending on a region where light in each wavelengthregion is mainly absorbed as described above, and a plurality of regionshaving a different composition ratio between the p-type and n-typesemiconductors may be included along the thickness direction of thelight-absorption layers 30 a, 30 b, and 30 c. Specific illustration isthe same as described above.

The drawing shows a structure in which the first organic photoelectronicdevice 100 a, the second organic photoelectronic device 100 b, and thethird organic photoelectronic device 100 c are sequentially stacked, butthe present disclosure is not limited thereto, and they may be stackedin various orders.

As described above, the first organic photoelectronic device 100 a, thesecond organic photoelectronic device 100 b, and the third organicphotoelectronic device 100 c have a stack structure, and thus the sizeof an image sensor may be reduced to realize a down-sized image sensor.In addition, as described above, a crosstalk due to unnecessaryadsorption of light in other wavelength regions except green may bereduced and sensitivity may be increased by improving green wavelengthselectivity in the light-absorption layer 30 of the organicphotoelectronic device 100.

The image sensor may be applied to, for example, various electronicdevices (e.g., a mobile phone or a digital camera), but is not limitedthereto.

Hereinafter, the present disclosure is illustrated in more detail withreference to examples. However, these are examples, and the presentdisclosure is not limited thereto.

Manufacture of Organic Photoelectronic Device Example 1

An about 150 nm-thick anode is formed by sputtering ITO on a glasssubstrate, and a 130 nm-thick light-absorption layer is formed thereonby codepositing2-((5-(naphthalen-1-yl(phenyl)amino)selenophen-2-yl)methylene)-1H-cyclopenta[b]naphthalene-1,3(2H)-dioneas a p-type semiconductor and C60 as an n-type semiconductor. Herein,the light-absorption layer is formed by changing the volume ratio of thep-type semiconductor and the n-type semiconductor to sequentially form a60 nm-thick lower layer including the p-type semiconductor and then-type semiconductor in a volume ratio of 1.25:1, a 40 nm-thick middlelayer including the p-type semiconductor and the n-type semiconductor ina volume ratio of 1.6:1, and a 30 nm-thick upper layer including thep-type semiconductor and the n-type semiconductor in a volume ratio of1.25:1. Subsequently, a molybdenum oxide (MoOx, 0<x≤3) thin film isdeposited to be 10 nm thick on the light-absorption layer. Then, a 7 nmthick cathode is formed on the molybdenum oxide thin film by sputteringITO, and a 40 nm-thick high refractive layer is formed by depositingaluminum oxide, manufacturing an organic photoelectronic device.

FIG. 19 shows light absorption curves of the p-type semiconductor,2-((5-(naphthalen-1-yl(phenyl)amino)selenophen-2-yl)methylene)-1H-cyclopenta[b]naphthalene-1,3(2H)-dioneand the n-type semiconductor, C60 depending on a wavelength.

Referring to FIG. 19, the p-type semiconductor,2-((5-(naphthalen-1-yl(phenyl)amino)selenophen-2-yl)methylene)-1H-cyclopenta[b]naphthalene-1,3(2H)-dioneis a light-absorbing material selectively absorbing light in awavelength region of about 500 to 600 nm, that is, light in a greenwavelength region, and the n-type semiconductor, C60 is alight-absorbing material absorbing light in a wavelength region of about400 to 600 nm, that is, light in a blue wavelength region and a greenwavelength region.

Example 2

An organic photoelectronic device is manufactured according to the samemethod as Example 1 except for forming an absorption layer including a60 nm-thick lower layer including the p-type semiconductor and then-type semiconductor in a volume ratio of 1.3:1, a 40 nm-thick middlelayer including the p-type semiconductor and the n-type semiconductor ina volume ratio of 1.6:1, and a 30 nm-thick upper layer including thep-type semiconductor and the n-type semiconductor in a volume ratio of1.3:1.

Example 3

An organic photoelectronic device is manufactured according to the samemethod as Example 1 except for forming an absorption layer including a60 nm-thick lower layer including the p-type semiconductor and then-type semiconductor in a volume ratio of 1.3:1, a 40 nm-thick middlelayer including the p-type semiconductor and the n-type semiconductor ina volume ratio of 1.9:1, and a 30 nm-thick upper layer including thep-type semiconductor and the n-type semiconductor in a volume ratio of1.3:1.

Comparative Example 1

An organic photoelectronic device is manufactured according to the samemethod as Example 1 except for forming a 130 nm-thick light-absorptionlayer by codepositing the p-type semiconductor and the n-typesemiconductor in a single volume ratio of 1.25:1.

Comparative Example 2

An organic photoelectronic device is manufactured according to the samemethod as Example 1 except for forming a 130 nm-thick light-absorptionlayer by codepositing the p-type semiconductor and the n-typesemiconductor in a single volume ratio of 1:1.

Comparative Example 3

An organic photoelectronic device is manufactured according to the samemethod as Example 1 except for forming an absorption layer including a60 nm-thick lower layer including the p-type semiconductor and then-type semiconductor in a volume ratio of 1:3, a 40 nm-thick middlelayer including the p-type semiconductor and the n-type semiconductor ina volume ratio of 1:1, and a 30 nm-thick upper layer including thep-type semiconductor and the n-type semiconductor in a volume ratio of3:1.

Comparative Example 4

An organic photoelectronic device is manufactured according to the samemethod as Example 1 except for forming a 130 nm-thick light-absorptionlayer by codepositing the p-type semiconductor and the n-typesemiconductor in a single volume ratio of 1.3:1.

Comparative Example 5

An organic photoelectronic device is manufactured according to the samemethod as Example 1 except for forming a 130 nm-thick light-absorptionlayer by codepositing the p-type semiconductor and the n-typesemiconductor in a single volume ratio of 1.39:1.

Comparative Example 6

An organic photoelectronic device is manufactured according to the samemethod as Example 1 except for forming a 130 nm-thick light-absorptionlayer by codepositing the p-type semiconductor and the n-typesemiconductor in a single volume ratio of 1.48:1.

Evaluation Evaluation 1

External quantum efficiencies of the organic photoelectronic devicesaccording to Example 1 and Comparative Example 1 depending on awavelength region are compared.

FIG. 13 is a graph showing the external quantum efficiencies of theorganic photoelectronic devices according to Example 1 and ComparativeExample 1 depending on a wavelength.

Referring to FIG. 13, the organic photoelectronic device according toExample 1 may secure external quantum efficiency (EQE) in a wavelengthregion of about 500 nm to 600 nm, that is, in a green wavelength regionbut reduced external quantum efficiency (EQE) in a wavelength region ofabout 400 nm to 500 nm, that is, in a blue wavelength region comparedwith the organic photoelectronic device according to ComparativeExample 1. Accordingly, wavelength selectivity of the organicphotoelectronic device according to Example 1 about the green wavelengthregion may be increased compared with the organic photoelectronic deviceaccording to Comparative Example 1.

Evaluation 2

External quantum efficiency changes of the organic photoelectronicdevices according to Example 1 and Comparative Examples 1 to 3 in thegreen wavelength region and the blue wavelength region are compared.

FIG. 14 is a graph showing external quantum efficiency in a greenwavelength region and a blue wavelength region of the organicphotoelectronic devices according to Example 1 and Comparative Example 1and FIG. 15 is a graph showing external quantum efficiency in a greenwavelength region and a blue wavelength region of the organicphotoelectronic devices according to Comparative Examples 2 and 3.

Referring to FIG. 14, the organic photoelectronic device according toExample 1 shows equivalent external quantum efficiency (EQE) in thegreen wavelength region but largely reduced external quantum efficiency(EQE) in the blue wavelength region compared with the organicphotoelectronic device according to Comparative Example 1. Accordingly,the wavelength selectivity of the organic photoelectronic deviceaccording to Example 1 about the green wavelength region may beincreased by lowering the external quantum efficiency of the organicphotoelectronic device about the blue wavelength region.

Referring to FIG. 15, the organic photoelectronic device according toComparative Example 2 shows substantially the same external quantumefficiency (EQE) in the green wavelength region as the external quantumefficiency (EQE) in the blue wavelength region, and the organicphotoelectronic device according to Comparative Example 3 shows muchreduced external quantum efficiency (EQE) in the green wavelength regioncompared with the organic photoelectronic device according toComparative Example 2. Accordingly, the organic photoelectronic devicesaccording to Comparative Examples 2 and 3 show low wavelengthselectivity about the green wavelength region, and in particular, theorganic photoelectronic device according to Comparative Example 3 showsmuch reduced external quantum efficiency (EQE) about the greenwavelength region.

Accordingly, wavelength selectivity of the organic photoelectronicdevice according to Example 1 may be increased by decreasing externalquantum efficiency of the blue wavelength region (EQE) as well assecuring external quantum efficiency (EQE) of the green wavelengthregion.

Evaluation 3

Optical simulations of the organic photoelectronic devices according toExample 2 and Comparative Example 4 are evaluated. The opticalsimulations are evaluated by using an MATLAB software.

EQE(λ)=Abs(λ)×CS(ratio)×CC(ratio)  [Equation 1]

The results are provided in FIGS. 16 and 17.

FIG. 16 is a simulation result of an absorption wavelength regiondepending on a position of light-absorption layer of the organicphotoelectronic device according to Example 2 and FIG. 17 is asimulation result of an absorption wavelength region depending on aposition of light-absorption layer of the organic photoelectronic deviceaccording to Comparative Example 4.

Referring to FIGS. 16 and 17, the organic photoelectronic deviceaccording to Example 2 turns out to less absorb light in the bluewavelength region compared with the organic photoelectronic deviceaccording to Comparative Example 4.

Evaluation 4

External quantum efficiency (EQE) decrease degrees of the organicphotoelectronic devices according to Examples 2 and 3 and ComparativeExamples 4 to 6 about the blue wavelength region at the maximum externalquantum efficiency (Max EQE) of the green wavelength region is predictedthrough a simulation.

The simulation is evaluated by using an MATLAB software.

$\begin{matrix}{{{EQE}(\lambda)} = {\sum\limits_{{n = 1},2,3}\left( {{{Abs}_{n}(\lambda)} \times {IQE}_{n}} \right)}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

The results are provided in Table 1.

TABLE 1 External quantum efficiency (EQE) of blue wavelength region @Max green EQE Example 2 19.9 Example 3 19.1 Comparative Example 4 21.1Comparative Example 5 20.5 Comparative Example 6 20.0

Referring to Table 1, the organic photoelectronic devices according toExamples 2 and 3 exhibit lower external quantum efficiency about theblue wavelength region at the maximum external quantum efficiency of thegreen wavelength region compared with the organic photoelectronicdevices according to Comparative Examples 4 to 6.

Evaluation 5

An image sensor is designed by respectively using the organicphotoelectronic devices according to Example 1 and Comparative Example1, and color difference and YSNR10 of the image sensor are evaluated.The image sensor is designed to have a structure shown in FIG. 9.

The color difference of the image sensor is evaluated in the followingmethod. A RGB raw signal obtained from the image sensor isimage-processed to reduce a difference from a real color. The imageprocessing consists of a white balance process of unifying intensity ofthe RGB raw signal and a color correction process of reducing a colordifference between an actual color of Macbeth chart (24 colors) and anoriginal color obtained from the image sensor. The color correctionprocess expresses a color by converting the RGB raw signal measured fromthe image sensor through a color correction matrix (CCM), and colorcharacteristics of the image sensor may be evaluated by digitalizing acolor difference of the converted color from the actual color of theMacbeth chart. The color difference indicates a difference from anactual color in the Macbeth chart, and as the color difference issmaller, a color may be closer to the actual color.

YSNR10 indicates luminance (unit: lux) that a signal and a noise have aratio of 10, and herein, the signal is sensitivity of a green signalafter the color correction process through the color correction matrix,and the noise is generated when the signal is measured in the imagesensor. As the YSNR10 is smaller, image characteristics are satisfactoryat low luminance.

The results are provided in FIG. 18.

FIG. 18 is graph showing color differences and YSNR10 of image sensorsto which the organic photoelectronic devices according to Example 1 andComparative Example 1 are applied

Referring to FIG. 18, an image sensor manufactured by applying theorganic photoelectronic device according to Example 1 exhibits a smallcolor difference and YSNR10 compared with an image sensor manufacturedby applying the organic photoelectronic device according to ComparativeExample 1. Accordingly, the image sensor manufactured by applying theorganic photoelectronic device according to Example 1 exhibits improvedwavelength selectivity and thus improved color display characteristicscompared with an image sensor manufactured by applying the organicphotoelectronic device according to Comparative Example 1.

Evaluation 6

Each image sensor is designed by respectively applying the organicphotoelectronic devices according to Example 1 and Comparative Example1, and its crosstalk is evaluated.

The image sensor is designed to have a structure shown in FIG. 9.

The crosstalk evaluation is performed as follows.

n and k of the absorption layers in the organic photoelectronic devicesaccording to Example 1 and Comparative Example 1 are obtained by usingSpectroscopic Ellipsometry. The n and k and the photoelectric conversionefficiency of a silicon photodiode and the organic photoelectronicdevice are used to obtain spectrum sensitivity of red photodiode, greenphotoelectronic device, and blue photodiode having the structure shownin FIG. 9 as FDTD (Finite Difference Time Domain). Herein, a wavelengthregion is divided into three regions of 440-480 nm (blue), 520-560 nm(green), and 590-630 nm (red), and then, how much other light conversiondevices in each color region are optically interfered is evaluated. Inother words, a relative integral of the sensitivity curved lines of thered and green light conversion devices in the 440-480 nm region based on100 of an integral of the sensitivity curved line of the blue lightconversion device in the 440-480 nm region. This relative integral is acrosstalk of the red and green light conversion devices about a blueregion in the 440-480 nm. Each of the crosstalks in the 520-560 nm andthe 590-630 nm is obtained in the same as above. Last, the 6measurements are averaged to obtain an average crosstalk.

The results are provided in Table 2.

TABLE 2 Average crosstalk (%) Example 1 25.1 Comparative Example 1 26.8

Referring to Table 2, an image sensor manufactured by applying theorganic photoelectronic device according to Example 1 exhibits a reducedaverage crosstalk and specifically, about 7% reduced average crosstalkcompared with an image sensor manufactured by applying the organicphotoelectronic device according to Comparative Example 1.

While this disclosure has been described in connection with what ispresently considered to be practical example embodiments, it is to beunderstood that the inventive concepts are not limited to the disclosedembodiments, but, on the contrary, are intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. An organic photoelectronic device, comprising: a first electrode and a second electrode facing each other; and a light-absorption layer between the first electrode and the second electrode, the light-absorption layer including, a first region closest to the first electrode, the first region having a first composition ratio (p₁/n₁) of a p-type semiconductor relative to an n-type semiconductor, a second region closest to the second electrode, the second region having a second composition ratio (p₂/n₂) of the p-type semiconductor relative to the n-type semiconductor, and a third region between the first region and the second region in a thickness direction, the third region having a third composition ratio (p₃/n₃) of the p-type semiconductor relative to the n-type semiconductor that is less than the first composition ratio (p₁/n₁) and the second composition ratio (p₂/n₂).
 2. The organic photoelectronic device of claim 1, wherein the first composition ratio (p₁/n₁) is the same as the second composition ratio (p₂/n₂).
 3. The organic photoelectronic device of claim 1, wherein the first composition ratio (p₁/n₁) is different from the second composition ratio (p₂/n₂).
 4. The organic photoelectronic device of claim 1, wherein a composition ratio (p/n) of the p-type semiconductor relative to the n-type semiconductor of the light-absorption layer is continuously decreased and then increased along the thickness direction.
 5. The organic photoelectronic device of claim 1, wherein a composition ratio (p/n) of the p-type semiconductor relative to the n-type semiconductor of the light-absorption layer is discontinuously decreased and then increased along the thickness direction.
 6. The organic photoelectronic device of claim 1, wherein the light-absorption layer is configured to absorb light in at least one part of a visible ray wavelength region; and a maximum light-absorption position of the light-absorption layer is different depending on the visible ray wavelength region.
 7. The organic photoelectronic device of claim 6, wherein the visible ray wavelength region includes first visible light and second visible light having a different wavelength region from the first visible light; the first visible light is absorbed at a maximum in one of the first region and the second region of the light-absorption layer; and the second visible light is absorbed at a maximum in the third region of the light-absorption layer.
 8. The organic photoelectronic device of claim 7, wherein one of the p-type semiconductor and the n-type semiconductor is a light-absorbing material configured to selectively absorb the first visible light; and the other of the p-type semiconductor and the n-type semiconductor is a light-absorbing material configured to absorb the first visible light and the second visible light.
 9. The organic photoelectronic device of claim 6, wherein the n-type semiconductor is the light-absorbing material configured to selectively absorb the first visible light; the p-type semiconductor is the light-absorbing material configured to absorb the first visible light and the second visible light; and the third composition ratio (p₃/n₃) is less than the first composition ratio (p₁/n₁) and the second composition ratio (p₂/n₂).
 10. The organic photoelectronic device of claim 1, wherein the third region includes the p-type semiconductor in a lesser amount than the first region and the second region.
 11. The organic photoelectronic device of claim 6, wherein the first visible light has a wavelength region of about 500 nm to about 600 nm; and the second visible light has a wavelength region of greater than or equal to about 380 nm and less than 500 nm.
 12. The organic photoelectronic device of claim 6, wherein one of the p-type semiconductor and the n-type semiconductor includes one of C60, C70, a derivative thereof, and a combination thereof.
 13. An image sensor comprising: the organic photoelectronic device of claim
 1. 14. The image sensor of claim 13, wherein the light-absorption layer is configured to absorb light in at least one part of a visible ray wavelength region; the visible ray wavelength region includes first visible light, second visible light, and third visible light, each of the first, second and third visible light having a different wavelength region; the organic photoelectronic device is configured to selectively absorb the first visible light; and the image sensor further comprises a semiconductor substrate integrated with a plurality of first photo-sensing devices configured to sense the second visible light and a plurality of second photo-sensing devices configured to sense the third visible light.
 15. The image sensor of claim 14, wherein the plurality of first photo-sensing devices and the plurality of second photo-sensing devices are spaced apart from each other in a horizontal direction.
 16. The image sensor of claim 15, further comprising: a first color filter overlapping the plurality of first photo-sensing devices, the first color filter configured to selectively transmit the second visible light; and a second color filter overlapping the plurality of second photo-sensing devices, the second color filter configured to selectively transmit the third visible light.
 17. The image sensor of claim 14, wherein the plurality of first photo-sensing devices and the plurality of second photo-sensing devices are spaced apart from each other in a vertical direction.
 18. The image sensor of claim 13, wherein the light-absorption layer is configured to absorb light in at least one part of a visible ray wavelength region; the visible ray wavelength region includes first visible light, second visible light, and third visible light, each of the first, second and third visible light having a different wavelength region; the organic photoelectronic device is a first organic photoelectronic device configured to selectively absorb the first visible light; the image sensor further comprises a second organic photoelectronic device configured to selectively absorb the second visible light and a third organic photoelectronic device configured to selectively absorb the third visible light; and the first organic photoelectronic device, the second organic photoelectronic device, and the third organic photoelectronic device are sequentially stacked.
 19. The image sensor of claim 14, wherein the first visible light has a wavelength region of about 500 nm to about 600 nm; the second visible light has a wavelength region of greater than or equal to about 380 nm and less than 500 nm; and the third visible light has a wavelength region of greater than about 600 nm and less than or equal to about 780 nm.
 20. The image sensor of claim 18, wherein the first visible light has a wavelength region of about 500 nm to about 600 nm; the second visible light has a wavelength region of greater than or equal to about 380 nm and less than 500 nm; and the third visible light has a wavelength region of greater than about 600 nm and less than or equal to about 780 nm.
 21. An electronic device comprising the image sensor of claim
 13. 22. An organic photoelectronic device comprising: a first electrode; a first light-absorption layer on the first electrode, the first light-absorption layer having a first composition ratio (p₁/n₁) of a p-type semiconductor relative to an n-type semiconductor; a second light-absorption layer on the first light-absorption layer, the second light-absorption layer having a second composition ratio (p₂/n₂) of the p-type semiconductor relative to the n-type semiconductor different from the first composition ratio (p₁/n₁); a third light-absorption layer on the second light-absorption layer, the third light-absorption layer having the first composition ratio (p₁/n₁); and a second electrode on the third light-absorption layer.
 23. The organic photoelectronic device of claim 22, wherein the second composition ratio (p₂/n₂) is less than the first composition ratio (p₁/n₁). 